#include <stdio.h>
#include <jpeglib.h>
#include <setjmp.h>
#include <stdlib.h>
#include "utils.h"

#define JPEG_QUALITY 50

typedef struct filestash_jpeg_error_mgr {
  struct jpeg_error_mgr pub;
  jmp_buf jmp;
} *filestash_jpeg_error_ptr;

void filestash_jpeg_error_exit (j_common_ptr cinfo);

int jpeg_to_jpeg(int inputDesc, int outputDesc, int targetSize) {
#ifdef HAS_DEBUG
  clock_t t;
  t = clock();
#endif
  int status = 0;
  FILE* input = fdopen(inputDesc, "rb");
  FILE* output = fdopen(outputDesc, "wb");
  if (!input || !output) {
    return 1;
  }

  struct jpeg_decompress_struct jpeg_config_input;
  struct jpeg_compress_struct jpeg_config_output;
  struct filestash_jpeg_error_mgr jerr;

  jpeg_config_input.err = jpeg_std_error(&jerr.pub);
  jpeg_config_output.err = jpeg_std_error(&jerr.pub);
  jpeg_config_input.dct_method = JDCT_IFAST;
  jpeg_config_input.do_fancy_upsampling = FALSE;
  jpeg_config_input.two_pass_quantize = FALSE;
  jpeg_config_input.dither_mode = JDITHER_ORDERED;

  jpeg_create_decompress(&jpeg_config_input);
  jpeg_create_compress(&jpeg_config_output);
  jpeg_stdio_src(&jpeg_config_input, input);
  jpeg_stdio_dest(&jpeg_config_output, output);

  jerr.pub.error_exit = filestash_jpeg_error_exit;
  if (setjmp(jerr.jmp)) {
    ERROR("exception");
    goto CLEANUP_AND_ABORT;
  }

  DEBUG("after constructor decompress");
  if(jpeg_read_header(&jpeg_config_input, TRUE) != JPEG_HEADER_OK) {
    status = 1;
    ERROR("not a jpeg");
    goto CLEANUP_AND_ABORT;
  }
  DEBUG("after header read");
  jpeg_config_input.dct_method = JDCT_IFAST;
  jpeg_config_input.do_fancy_upsampling = FALSE;
  jpeg_config_input.two_pass_quantize = FALSE;
  jpeg_config_input.dither_mode = JDITHER_ORDERED;
  jpeg_calc_output_dimensions(&jpeg_config_input);

  int image_min_size = min(jpeg_config_input.output_width, jpeg_config_input.output_height);
  jpeg_config_input.scale_num = 1;
  jpeg_config_input.scale_denom = 1;
  int targetSizeAbs = abs(targetSize);
  if (image_min_size / 8 >= targetSizeAbs) {
    jpeg_config_input.scale_num = 1;
    jpeg_config_input.scale_denom = 8;
  } else if (image_min_size * 2 / 8 >= targetSizeAbs) {
    jpeg_config_input.scale_num = 1;
    jpeg_config_input.scale_denom = 4;
  } else if (image_min_size * 3 / 8 >= targetSizeAbs) {
    jpeg_config_input.scale_num = 3;
    jpeg_config_input.scale_denom = 8;
  } else if (image_min_size * 4 / 8 >= targetSizeAbs) {
    jpeg_config_input.scale_num = 4;
    jpeg_config_input.scale_denom = 8;
  } else if (image_min_size * 5 / 8 >= targetSizeAbs) {
    jpeg_config_input.scale_num = 5;
    jpeg_config_input.scale_denom = 8;
  } else if (image_min_size * 6 / 8 >= targetSizeAbs) {
    jpeg_config_input.scale_num = 6;
    jpeg_config_input.scale_denom = 8;
  } else if (image_min_size * 7 / 8 >= targetSizeAbs) {
    jpeg_config_input.scale_num = 7;
    jpeg_config_input.scale_denom = 8;
  }

  DEBUG("start decompress");
  if(jpeg_start_decompress(&jpeg_config_input) == FALSE) {
    ERROR("jpeg_start_decompress");
    status = 1;
    goto CLEANUP_AND_ABORT;
  }
  DEBUG("processing image setup");
  int jpeg_row_stride = jpeg_config_input.output_width * jpeg_config_input.output_components;
  jpeg_config_output.image_width = jpeg_config_input.output_width;
  jpeg_config_output.image_height = jpeg_config_input.output_height;
  jpeg_config_output.input_components = jpeg_config_input.num_components;
  jpeg_config_output.in_color_space = jpeg_config_input.out_color_space;
  jpeg_set_defaults(&jpeg_config_output);
  jpeg_set_quality(&jpeg_config_output, JPEG_QUALITY, TRUE);
  jpeg_start_compress(&jpeg_config_output, TRUE);
  JSAMPARRAY buffer = jpeg_config_input.mem->alloc_sarray((j_common_ptr) &jpeg_config_input, JPOOL_IMAGE, jpeg_row_stride, 1);

  DEBUG("processing image");
  while (jpeg_config_output.next_scanline < jpeg_config_output.image_height) {
    jpeg_read_scanlines(&jpeg_config_input, buffer, 1);
    jpeg_write_scanlines(&jpeg_config_output, buffer, 1);
  }

  DEBUG("end decompress");
  jpeg_finish_decompress(&jpeg_config_input);
  DEBUG("finish decompress");
  jpeg_finish_compress(&jpeg_config_output);

 CLEANUP_AND_ABORT:
  jpeg_destroy_decompress(&jpeg_config_input);
  jpeg_destroy_compress(&jpeg_config_output);
  DEBUG("final");
  return status;
}

void filestash_jpeg_error_exit (j_common_ptr cinfo) {
  filestash_jpeg_error_ptr filestash_err = (filestash_jpeg_error_ptr) cinfo->err;
  longjmp(filestash_err->jmp, 1);
}